/*
  Red Black Trees
  (C) 1999  Andrea Arcangeli <andrea@suse.de>
  (C) 2002  David Woodhouse <dwmw2@infradead.org>
  
  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation; either version 2 of the License, or
  (at your option) any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

  linux/lib/rbtree.c
*/

#include "rbtree.h"

static void __rb_rotate_left(struct rb_node *node, struct rb_root *root)
{
    struct rb_node *right = node->rb_right;
    struct rb_node *parent = rb_parent(node);

    if ((node->rb_right = right->rb_left))
	rb_set_parent(right->rb_left, node);
    right->rb_left = node;

    rb_set_parent(right, parent);

    if (parent)
    {
	if (node == parent->rb_left)
	    parent->rb_left = right;
	else
	    parent->rb_right = right;
    }
    else
	root->rb_node = right;
    rb_set_parent(node, right);
}

static void __rb_rotate_right(struct rb_node *node, struct rb_root *root)
{
    struct rb_node *left = node->rb_left;
    struct rb_node *parent = rb_parent(node);

    if ((node->rb_left = left->rb_right))
	rb_set_parent(left->rb_right, node);
    left->rb_right = node;

    rb_set_parent(left, parent);

    if (parent)
    {
	if (node == parent->rb_right)
	    parent->rb_right = left;
	else
	    parent->rb_left = left;
    }
    else
	root->rb_node = left;
    rb_set_parent(node, left);
}

void rb_insert_color(struct rb_node *node, struct rb_root *root)
{
    struct rb_node *parent, *gparent;

    while ((parent = rb_parent(node)) && rb_is_red(parent))
    {
	gparent = rb_parent(parent);

	if (parent == gparent->rb_left)
	{
	    {
		register struct rb_node *uncle = gparent->rb_right;
		if (uncle && rb_is_red(uncle))
		{
		    rb_set_black(uncle);
		    rb_set_black(parent);
		    rb_set_red(gparent);
		    node = gparent;
		    continue;
		}
	    }

	    if (parent->rb_right == node)
	    {
		register struct rb_node *tmp;
		__rb_rotate_left(parent, root);
		tmp = parent;
		parent = node;
		node = tmp;
	    }

	    rb_set_black(parent);
	    rb_set_red(gparent);
	    __rb_rotate_right(gparent, root);
	} else {
	    {
		register struct rb_node *uncle = gparent->rb_left;
		if (uncle && rb_is_red(uncle))
		{
		    rb_set_black(uncle);
		    rb_set_black(parent);
		    rb_set_red(gparent);
		    node = gparent;
		    continue;
		}
	    }

	    if (parent->rb_left == node)
	    {
		register struct rb_node *tmp;
		__rb_rotate_right(parent, root);
		tmp = parent;
		parent = node;
		node = tmp;
	    }

	    rb_set_black(parent);
	    rb_set_red(gparent);
	    __rb_rotate_left(gparent, root);
	}
    }

    rb_set_black(root->rb_node);
}

static void __rb_erase_color(struct rb_node *node, struct rb_node *parent,
			     struct rb_root *root)
{
    struct rb_node *other;

    while ((!node || rb_is_black(node)) && node != root->rb_node)
    {
	if (parent->rb_left == node)
	{
	    other = parent->rb_right;
	    if (rb_is_red(other))
	    {
		rb_set_black(other);
		rb_set_red(parent);
		__rb_rotate_left(parent, root);
		other = parent->rb_right;
	    }
	    if ((!other->rb_left || rb_is_black(other->rb_left)) &&
		(!other->rb_right || rb_is_black(other->rb_right)))
	    {
		rb_set_red(other);
		node = parent;
		parent = rb_parent(node);
	    }
	    else
	    {
		if (!other->rb_right || rb_is_black(other->rb_right))
		{
		    struct rb_node *o_left;
		    if ((o_left = other->rb_left))
			rb_set_black(o_left);
		    rb_set_red(other);
		    __rb_rotate_right(other, root);
		    other = parent->rb_right;
		}
		rb_set_color(other, rb_color(parent));
		rb_set_black(parent);
		if (other->rb_right)
		    rb_set_black(other->rb_right);
		__rb_rotate_left(parent, root);
		node = root->rb_node;
		break;
	    }
	}
	else
	{
	    other = parent->rb_left;
	    if (rb_is_red(other))
	    {
		rb_set_black(other);
		rb_set_red(parent);
		__rb_rotate_right(parent, root);
		other = parent->rb_left;
	    }
	    if ((!other->rb_left || rb_is_black(other->rb_left)) &&
		(!other->rb_right || rb_is_black(other->rb_right)))
	    {
		rb_set_red(other);
		node = parent;
		parent = rb_parent(node);
	    }
	    else
	    {
		if (!other->rb_left || rb_is_black(other->rb_left))
		{
		    register struct rb_node *o_right;
		    if ((o_right = other->rb_right))
			rb_set_black(o_right);
		    rb_set_red(other);
		    __rb_rotate_left(other, root);
		    other = parent->rb_left;
		}
		rb_set_color(other, rb_color(parent));
		rb_set_black(parent);
		if (other->rb_left)
		    rb_set_black(other->rb_left);
		__rb_rotate_right(parent, root);
		node = root->rb_node;
		break;
	    }
	}
    }
    if (node)
	rb_set_black(node);
}

void rb_erase(struct rb_node *node, struct rb_root *root)
{
    struct rb_node *child, *parent;
    int color;

    if (!node->rb_left)
	child = node->rb_right;
    else if (!node->rb_right)
	child = node->rb_left;
    else
    {
	struct rb_node *old = node, *left;

	node = node->rb_right;
	while ((left = node->rb_left) != NULL)
	    node = left;
	child = node->rb_right;
	parent = rb_parent(node);
	color = rb_color(node);

	if (child)
	    rb_set_parent(child, parent);
	if (parent == old) {
	    parent->rb_right = child;
	    parent = node;
	} else
	    parent->rb_left = child;

	node->rb_parent_color = old->rb_parent_color;
	node->rb_right = old->rb_right;
	node->rb_left = old->rb_left;

	if (rb_parent(old))
	{
	    if (rb_parent(old)->rb_left == old)
		rb_parent(old)->rb_left = node;
	    else
		rb_parent(old)->rb_right = node;
	} else
	    root->rb_node = node;

	rb_set_parent(old->rb_left, node);
	if (old->rb_right)
	    rb_set_parent(old->rb_right, node);
	goto color;
    }

    parent = rb_parent(node);
    color = rb_color(node);

    if (child)
	rb_set_parent(child, parent);
    if (parent)
    {
	if (parent->rb_left == node)
	    parent->rb_left = child;
	else
	    parent->rb_right = child;
    }
    else
	root->rb_node = child;

color:
    if (color == RB_BLACK)
	__rb_erase_color(child, parent, root);
}

/*
 * This function returns the first node (in sort order) of the tree.
 */
struct rb_node *rb_first(struct rb_root *root)
{
    struct rb_node	*n;

    n = root->rb_node;
    if (!n)
	return NULL;
    while (n->rb_left)
	n = n->rb_left;
    return n;
}

struct rb_node *rb_last(struct rb_root *root)
{
    struct rb_node	*n;

    n = root->rb_node;
    if (!n)
	return NULL;
    while (n->rb_right)
	n = n->rb_right;
    return n;
}

struct rb_node *rb_next(struct rb_node *node)
{
    struct rb_node *parent;

    if (rb_parent(node) == node)
	return NULL;

    /* If we have a right-hand child, go down and then left as far
       as we can. */
    if (node->rb_right) {
	node = node->rb_right; 
	while (node && node->rb_left)
	    node=node->rb_left;
	return node;
    }

    /* No right-hand children.  Everything down and left is
       smaller than us, so any 'next' node must be in the general
       direction of our parent. Go up the tree; any time the
       ancestor is a right-hand child of its parent, keep going
       up. First time it's a left-hand child of its parent, said
       parent is our 'next' node. */
    while ((parent = rb_parent(node)) && node == parent->rb_right)
	node = parent;

    return parent;
}

struct rb_node *rb_prev(struct rb_node *node)
{
    struct rb_node *parent;

    if (rb_parent(node) == node)
	return NULL;

    /* If we have a left-hand child, go down and then right as far
       as we can. */
    if (node->rb_left) {
	node = node->rb_left; 
	while (node->rb_right)
	    node=node->rb_right;
	return node;
    }

    /* No left-hand children. Go up till we find an ancestor which
       is a right-hand child of its parent */
    while ((parent = rb_parent(node)) && node == parent->rb_left)
	node = parent;

    return parent;
}

void rb_replace_node(struct rb_node *victim, struct rb_node *new_node,
		     struct rb_root *root)
{
    struct rb_node *parent = rb_parent(victim);

    /* Set the surrounding nodes to point to the replacement */
    if (parent) {
	if (victim == parent->rb_left)
	    parent->rb_left = new_node;
	else
	    parent->rb_right = new_node;
    } else {
	root->rb_node = new_node;
    }
    if (victim->rb_left)
	rb_set_parent(victim->rb_left, new_node);
    if (victim->rb_right)
	rb_set_parent(victim->rb_right, new_node);

    /* Copy the pointers/colour from the victim to the replacement */
    *new_node = *victim;
}
